This invention relates to a method of operating an engine and an engine apparatus and more particularly to an improved method and apparatus for operating an engine in response to actual conditions in the combustion chamber during each combustion cycle and for measuring certain operating parameters of the engine on a cycle to cycle basis.
With the modern technology and electronics, many of the components and running conditions of an internal combustion engine can be controlled more accurately than with previous mechanical systems. For example, the control of the fuel/air ratio, spark timing and other adjustable factors of engine operation are greatly facilitated through the use of electronic components and electronic computers. However, in order to accurately sense the running of the engine and the combustion during each combustion cycle, it is necessary to provide a sensor that is directly positioned within the combustion chamber or in proximity to it and which senses the actual combustion conditions in the engine. Most engine controls employ external devices such as oxygen sensors or knock sensors which actually sense only average conditions due to their inherent nature. Also in-cylinder pressure transducers have been proposed for these purposes.
It has been understood that knocking can be determined by an optical sensor that operates within the combustion chamber and which senses the luminosity of the gases in that chamber. A wide variety of knock sensors have been proposed that employ such sensors. However, the inventors have discovered that luminosity in the combustion chamber can indicate a much wider range of running conditions than previously realized.
As has been previously noted, in-cylinder pressure transducers have been proposed for providing signals to be utilized in engine control. This indicates a recognition of the importance of measuring the actual running and operating condition within the individual cylinders. Even though luminosity devices have been well known, it has not been previously recognized that the luminosity device can be employed for measuring other characteristics of the engine. The disadvantage with the use of pressure transducers is that they must exist in a very hostile environment and can provide only limited information. Pressure transducers are very sensitive to temperature and, as is well known, the temperature in the combustion chamber fluctuates widely during engine operation. Hence the pressure signal can be very adversely effected by these temperature changes. In addition, the pressure transducers require the conversion of a pressure signal into an electrical signal and this electrical signal then must be transmitted to a remote location in order to provide the desired information. Obviously, such devices are prone to false readings due to the extraneous electrical noise that can be generated within an engine during its running operation. Furthermore, the amount of information which can be received from such pressure transducers is, as noted, severely limited.
It is, therefore, a principal object of this invention to provide an improved system and method for operating an engine wherein the engine adjustable parameters can be varied in response to actual sensed conditions in the combustion chamber during each combustion cycle.
It is a further object of this invention to provide an engine control system wherein the engine can be controlled in response to actual combustion conditions occurring in the combustion chamber on individual cycles.
Because of the aforenoted averaging tendency of the prior art type of sensors, it is also difficult to determine the existence of cylinder to cylinder or cycle to cycle variation. It is, therefore, a still further object of this invention to provide an improved system for sensing engine operation and sensing and determining cycle to cycle and chamber to chamber variations during running.
In addition to controlling the engine, the control should be predicated upon certain measured parameters of the engine. For example, it is very desirable to be able to obtain and measure such engine running characteristics as maximum cylinder pressure and cylinder pressure in relation to crank angle, maximum heat release and the relationship of heat release to crank angle, air/fuel ratio and indicated mean effective pressure (IMEP) which is in effect the same as measuring engine torque or power. However, it has not been previously possible to measure such values, particularly when the engine is running on a cycle to cycle basis with a simple and yet engine mounted sensor.
It is, therefore, a further object of this invention to provide an improved and simplified arrangement for measuring the aforenoted characteristics of an engine during its running and on a cycle to cycle basis through the use of a simple sensor that is mounted directly on the engine.
A type of engine sensor has been proposed that senses the actual luminosity of the gases within the combustion chamber. A wide variety of patents illustrating and describing the use of such sensors have issued including the following:
U.S. Pat. Nos. 4,358,952
4,369,748
4,377,086
4,393,687
4,409,815
4,412,446
4,413,509
4,419,212
4,422,321
4,422,323
4,425,788
4,468,949
4,444,043
4,515,132
For the most part, these patents disclose arrangements wherein the sensor is utilized to sense only total luminosity and to equate the luminosity signal to a knocking signal.
However and as has been noted, the inventors have discovered that this signal can also be employed to sense a wide variety of other engine running characteristics and it is a further object of this invention to measure these characteristics, use these signals to control the engine parameters to obtain better running and to obtain consistent running from cylinder to cylinder and cycle to cycle.